Antistatic packaging based on PTT/PTT-g-MA/ABS/MWCNT nanocomposites: Effect of the chemical functionalization of MWCNTs

Polymer/carbon nanotube nanocomposites have attracted high interest for a wide spectrum of applications, including antistatic packaging used to protect electronic devices against electrostatic discharge. Polytrimethylene terephthalate (PTT)/maleic-anhydride-grafted PTT (PTT-g-MA)/acrylonitrile butadiene styrene (ABS) blend-based multiwall carbon nanotubes (MWCNTs) nanocomposites were prepared through extrusion. It was conducted chemical functionalization on the MWCNTs by oxidation using nitric acid to introduce functional groups. The effect of the amount (0.5 or 1.0 wt%) and functionalization of MWCNTs on the nanocomposites was investigated. Despite the poor barrier properties of PTT/PTT-g-MA/ABS/MWCNT nanocomposites due to the presence of voids confirmed by scanning electron microscopy (SEM), the nanocomposites with functionalized MWCNT (MWCNTf) showed excellent barrier properties, indicating that the functionalization process improved the interaction between the MWCNTs and the matrix. The addition of MWCNTs into PTT/PTT-g-MA/ABS blend decreased the electrical resistivity by eight orders of magnitude. The use of MWCNTf may still disrupt the electrical network pathway and slightly decreasing the electrical resistivity, but the nanocomposites present the desired properties required for antistatic packaging.     

FB3-F银钎剂去膜机理

研究了由H₃BO₃、K₂B₄O₇和KF（质量比为7:10:3）3种组分配制而成的银钎剂的去膜机理。结果表明：在700 ℃时,K₂B₄O₇或KF都不能单独去除Q235钢板表面的氧化膜,且KF会加快高温下钢表面的氧化速率;H₃BO₃能够去除Q235钢表面的氧化膜,然而其反应产物具有明显的非晶结构特征,并且流动性差。此外在700 ℃时,H₃BO₃与KF能够发生反应,其反应产物可以去除钢表面氧化膜。KF和K₂B₄O₇之间也能在700 ℃发生类似的反应,然而其反应产物非常坚硬。因此,在700 ℃时,H₃BO₃、K₂B₄O₇和KF混合钎剂能够与Q235钢板表面氧化膜反应,且反应产物具有明显的非晶特征。KF的加入将非反应性H₃BO₃-K₂B₄O₇二元体系转化为反应性KF-H₃BO₃-K₂B₄O₇三元体系。在这个三元体系中,KF不但对钢板没有腐蚀性,反而促进了氧化膜的去除。     

基于紧密堆积理论优化超高性能混凝土钢纤维参数

基于改良的Andreasen & Andersen 颗粒堆积模型优化设计了超高性能混凝土(UHPC)的基础配合比,研究了钢纤维的形状、含量及混杂钢纤维对UHPC湿堆积密实度的影响。然后采用D-最优设计(DOD)方法,预测和评估混杂钢纤维对UHPC湿堆积密实度的影响,并基于DOD模型优化设计了UHPC的最佳钢纤维掺量。结果表明,长直纤维、短直纤维、端钩纤维的掺入会对UHPC堆积体系、密实度带来不同程度的影响,其中端钩纤维对UHPC密实度的降低程度最大。此外,钢纤维掺量与UHPC堆积体系也有一定关系,当纤维掺量超过2.0%(体积分数,下同)时,UHPC的密实度急剧下降,造成UHPC堆积体系的显著破坏;基于建立的DOD优化模型分析得出,0.9%的长直纤维与1.1%端钩纤维为最佳纤维混杂方式,可使得钢纤维对UHPC堆积体系的扰乱作用最小化。     

采用遗传相关向量机的工业机器人焊缝跟踪预测

为了克服传统焊缝跟踪方法精度低的问题,提出基于遗传相关向量机(G-RVM)的工业机器人焊缝跟踪预测方法,其中应用遗传算法对相关向量机参数进行优化。相关向量机通过构建回归函数以解决焊缝跟踪问题。为验证所设计控制器的有效性,进行了焊缝的跟踪实验,并设计了实验条件。实验结果表明,基于遗传相关向量机的焊缝跟踪误差小于支持向量机法所得数据。可见采用遗传相关向量机的控制更能够适应实际焊接过程的变化。     

膨胀石墨填充SBS复合材料的界面相互作用

膨胀石墨（ＥＧ）填充量小于２５％时,ＥＧ／ＳＢＳ复合材料的拉伸强度随ＥＧ充量的增加而增加,最大拉伸强度达２７．８ＭＰａ;而在ＥＧ填充量为１０％时,复合材料的扯断伸长率达到最大值（７８５％）,随后开始下降。用二甲苯作溶剂,在１４５℃抽提ＥＧ／ＳＢＳ复合材料２４ｈ后,复合材料中形成了稳定的交联结构,同时,凝胶含量随ＥＧ填充量的增加而增加。由此说明复合物中ＥＧ与ＳＢＳ之间产生了强烈的界面相互作用。ＤＭＡ     

基于委托代理的铁路建设项目施工组织模式问题分析——以某项目架子队管理模式为例

架子队经证实是一种适合我国目前高速铁路建设高要求的新型施工组织模式,较之传统的劳务分包模式在工程质量、安全、劳务人员管理等方面更加可控.通过对施工企业、劳务公司、劳务人员这三个劳务供求的主要利益相关方之间的博弈关系进行分析,认为标准化管理思想可以有效地控制架子队模式下的新型委托代理关系中所存在的各种风险,并用案例加以证...     

Separation of cisplatin and its hydrolysis products using electrospray ionization high-field asymmetric waveform ion mobility spectrometry coupled with ion trap mass spectrometry

Cisplatin and its mono- and dihydrated complexes have been separated using a high-field asymmetric waveform ion mobility spectrometry (FAIMS) analyzer interfaced with electrospray ionization (ESI) and ion trap mass spectrometry (ITMS). The addition of helium to the nitrogen curtain/carrier gas in the FAIMS device improved both the sensitivity and selectivity of the electrospray analysis. Introduction of a three-component mixture as curtain/carrier gas, nitrogen, helium, and carbon dioxide, resulted in further improvements to sensitivity. Compared with conventional ESI-MS, the background chemical noise in the ESI-FAIMS-ITMS spectrum was dramatically reduced, resulting in over 30-fold improvement in the signal-to-noise ratio for cisplatin. Analytical results were linear over the concentration range 10-200 ng/mL for intact cisplatin with a corresponding detection limit determined of 0.7 ng/mL with no derivatization or chromatographic separation prior to analysis.     

A clamped punch-loaded blister test for adhesion: a lumped parameter model and the bending-to-stretching behavior

This paper presents a clamped punch-loaded blister test and the corresponding lumped parameter model for the adhesion between thin film and rigid substrate. In the test, circular thin film is adhered to rigid substrate and an external load is applied with a clamped punch to cause the deflection of thin film. The relations among load, deflection, residual stress and strain energy release rate are thoroughly investigated. Analytical solutions in linear and nonlinear behaviors are obtained and the bending and stretching effects are associated through a lumped parameter model. The result of lumped-parameter model shows that the blister deflection is directly proportional to the applied load in the linear bending dominant region and the blister deflection is in direct proportion to the cubic root of the applied load in the nonlinear stretching dominant region. This has been proved by the result of nonlinear finite element analysis and the experimental result as well.     

探讨计数器设计的授课思路与方法

根据作者多年来的教学实践经验，探讨了数字逻辑电路中二进制、十进制和任意进制计数器设计方面的一些授课思路与方法。     

Human Adipose-Derived Mesenchymal Progenitor Cells Engraft into Rabbit Articular Cartilage

Mesenchymal stem cells (MSCs) are known to have the potential for articular cartilage regeneration, and are suggested for the treatment of osteoarthritis (OA). Here, we investigated whether intra-articular injection of xenogeneic human adipose-derived mesenchymal progenitor cells (haMPCs) promoted articular cartilage repair in rabbit OA model and engrafted into rabbit articular cartilage. The haMPCs were cultured in vitro, and phenotypes and differentiation characteristics of cells were evaluated. OA was induced surgically by anterior cruciate ligament transection (ACLT) and medical meniscectomy of knee joints. At six weeks following surgery, hyaluronic acid (HA) or haMPCs was injected into the knee joints, the contralateral knee served as normal control. All animals were sacrificed at the 16th week post-surgery. Assessments were carried out by macroscopic examination, hematoxylin/eosin (HE) and Safranin-O/Fast green stainings and immunohistochemistry. The data showed that haMPC treatment promoted cartilage repair. Signals of human mitochondrial can be directly detected in haMPC treated cartilage. The haMPCs expressed human leukocyte antigen I (HLA-I) but not HLA-II-DR in vivo. These results suggest that intra-articular injection of haMPCs promotes regeneration of articular cartilage in rabbit OA model, and support the notion that MPCs are transplantable between HLA-incompatible individuals.